Apparatus for driving a bone fixation pin

ABSTRACT

A bone fixation pin is inserted into a bone with an apparatus comprising a housing having a proximal portion and a distal portion, the distal portion having an inner surface and an opening configured to receive the bone fixation pin; a drive shaft having a proximal end configured to engage a handle and a distal end; and a body having an axis and a peripheral edge. The body comprises a bore along the axis, the bore being configured to slidably engage the distal end of the drive shaft; and a plurality of evenly spaced slots in the peripheral edge of the body. A plurality of chuck arms move radially along the evenly spaced slots in the peripheral edge of the body, each chuck arm having an inner surface and an outer surface, with each chuck arm being biased toward the axis of the body by a first biasing force. The outer surface of each chuck arm slidably engages the inner surface of the housing. The distal end of the drive shaft and the body are within the proximal portion of the housing, with the body being biased toward the distal end of the housing by a second biasing force. Each chuck arm has an engaging surface configured to engage a head of the bone fixation pin, where pressure applied to the engaging surface drives the chuck arms in a radial direction against the first biasing force, and simultaneously drives the body carrying the chuck arms axially against the second biasing force.

BACKGROUND 1. Field of the Disclosure

This disclosure relates generally to devices for positioning bone fixation pins or screws in a bone. More particularly, this disclosure relates generally to devices for positioning bone fixation pins or screws having differing diameters in bones using a single tool.

2. Description of Related Art

Bone fixation pins, screws, and the like are produced in a variety of diameters. Such pins are positioned in a bone, or used to hold multiple bones or bone fragments together. Such pins or screws are manipulated using chucks having movable chuck arms which grip the shaft of a pin or screw.

In a surgical environment, it is desirable to be able to quickly insert and remove bone fixation pins or screws from a chuck, without spending time manipulating the chuck to ensure that the chuck arms properly grip the pin. Further, it is often necessary to use multiple pins having different diameters in a single procedure or a single operation. A single chuck which can accommodate pins having a variety of diameters would save time in the operating theater, as the operating team would not have to ensure that the proper chuck is matched to each pin.

A variety of adjustable chucks are known in the art. However, many of these chuck arms require manipulation of the chuck body to open or close the chuck arms. In some cases, the inner surface of the chuck body has threading which mates with threading provided on the outer surfaces of the chuck arms. Rotation of the chuck body then causes axial movement of the chuck arms. In other cases, the chuck arms engage an inner surface of the chuck body, so axial movement of the chuck body causes radial movement of the chuck arms. However, it would be preferable to position a bone fixation pin on a chuck quickly, without requiring manual manipulation of the chuck.

SUMMARY

In light of the present need for improved tools or chucks for manipulating bone fixation pins or screws, a brief summary of various embodiments is presented. Some simplifications and omissions may be made in the following summary, which is intended to highlight and introduce some aspects of various embodiments, but not to limit the scope of the invention. Detailed descriptions of various embodiments adequate to allow those of ordinary skill in the art to make and use the inventive concepts will follow in later sections.

Various embodiments disclosed herein relate to an apparatus for inserting a bone fixation pin having a rounded, conical, or frustoconical head and a cylindrical body into a bone. The apparatus includes a housing having a proximal portion and a distal portion, the distal portion having a conical inner surface and an opening configured to receive the bone fixation pin; a drive shaft having a proximal end configured to engage a handle and a distal end; and a body having an axis and a peripheral edge. The body includes a bore along the axis of the body, where the bore may slidably engage the distal end of the drive shaft; and a plurality of evenly spaced slots in a peripheral edge of the body. A plurality of chuck arms, each chuck arm is adapted to move radially along one of the evenly spaced slots in the peripheral edge of the body, with chuck arm having an inner surface and an outer surface. In various embodiments, the distal end of the drive shaft and the body are within the proximal portion of the housing, with the body being biased toward the distal end of the housing by a biasing force. In various embodiments, the biasing force is applied by a spring. The inner surface of each chuck arm is configured to engage the bone fixation pin, and the outer surface of each chuck arm slidably engages the conical inner surface of the housing. In various embodiments, the proximal end of the drive shaft has a conical or frustoconical opening configured to receive the rounded, conical, or frustoconical head of the bone fixation pin.

In various embodiments, the inner surface of each chuck arm comprises a sloped lower surface configured to engage the rounded, conical, or frustoconical head of the bone fixation pin; and an upper surface parallel to the axis of the body. The upper surface is configured to engage the cylindrical body of the bone fixation pin. The apparatus is configured to receive a bone fixation pin through the opening in the housing until the head of the pin engages the opening in the proximal end of the drive shaft. Contact between the head of the bone fixation pin and the sloped lower surfaces of the chuck arms then pushes the chuck arms radially outward in the slots in the peripheral edge of the body; and radial movement of the chuck arms causes the chuck arms to slidably move along the conical inner surface of the housing, pushing the body axially toward the proximal end of the housing, until the bone fixation pin is held in position by the inner surfaces of the chuck arms and the force biasing the body toward the distal end of the housing.

Various embodiments disclosed herein relate to an apparatus for inserting a bone fixation pin into a bone, the pin having a rounded, conical, or frustoconical head and a cylindrical body having a body diameter. The apparatus includes a housing having a proximal portion and a distal portion, the distal portion having a stepped inner surface and an opening configured to receive the bone fixation pin. Each step in the stepped inner surface may have a lower edge which is sloped toward an axis of the housing; and an inner edge having a surface which is parallel to the axis of the housing. The apparatus further includes a drive shaft having a proximal end configured to engage a handle and a distal end; and a body having an axis and a peripheral edge. The body includes a bore along the axis, said bore being configured to slidably engage the distal end of the drive shaft; and a plurality of evenly spaced slots in the peripheral edge of the body. The evenly spaced slots are configured to receive a plurality of chuck arms, where each chuck arm is adapted to move radially along one of the evenly spaced slots in the peripheral edge of the body. Each chuck arm has an inner surface and a lower tip. The distal end of the drive shaft and the body are within the proximal portion of the housing, said body being biased toward the distal end of the housing, possibly by a spring. The inner surface of each chuck arm is configured to engage the bone fixation pin, and the lower tip of each chuck arm slidably engages a first step on the stepped inner surface of the housing.

In various embodiments, the proximal end of the drive shaft has a conical or frustoconical opening configured to receive the head of the bone fixation pin. The inner surface of each chuck arm comprises a sloped lower surface configured to engage the rounded, conical, or frustoconical head of the bone fixation pin; and an upper surface parallel to the axis of the body, the upper surface being configured to engage the cylindrical body of the bone fixation pin. In various embodiments, the apparatus is configured to receive a bone fixation pin through the opening in the housing until the head of the pin engages the opening in the proximal end of the drive shaft. Contact between the head of the bone fixation pin and the sloped lower surfaces of the chuck arms pushes the chuck arms axially toward the proximal end of the housing. In various embodiments, this axial movement causes the lower tip of each chuck arm to disengage from the first step on the stepped inner surface of the housing and engage a second step on the stepped inner surface. The chuck arms are configured to engage the cylindrical body of the bone fixation pin when the lower tip of each chuck arm engages the second step on the stepped inner surface.

In various embodiments, the stepped inner surface of the housing comprises a second step and a third step, the second and third steps being configured to be sequentially engaged by the lower tip of each chuck arm as the chuck arms move toward the proximal end of the housing. The chuck arms are configured to engage the cylindrical body of a bone fixation pin having a first body diameter when the lower tip of each chuck arm engages the second step on the stepped inner surface; and to engage the cylindrical body of a bone fixation pin having a second body diameter when the lower tip of each chuck arm engages the third step on the stepped inner surface.

Various embodiments disclosed herein are directed to an apparatus for inserting a bone fixation pin having a head and a body having a cylindrical portion, including a housing having a proximal portion and a distal portion, the distal portion having a conical inner surface and an opening configured to receive the bone fixation pin; a drive shaft having a proximal end configured to engage a handle and a distal end; and a body having an axis and a peripheral edge. In various embodiments, the body includes a bore along the axis, the bore being configured to slidably engage the distal end of the drive shaft; and a plurality of spaced slots in the peripheral edge of the body. A plurality of chuck arms having an inner surface and an outer surface may engage the body, with each chuck arm being configured to move radially along one of the spaced slots in the peripheral edge of the body.

In various embodiments, each chuck arm is biased toward the axis of the body by a first biasing force. The first biasing force may be applied by a spring having a first spring force. The spring may be a garter spring, with the garter spring being circular and mounted on a set of spring mounting surfaces. Each spring mounting surface is on an outer surface of one of the chuck arms.

In various embodiments, the distal end of the drive shaft and the body are within the proximal portion of the housing, with the body being biased toward the distal end of the housing by a second biasing force. The second biasing force may be applied by a spring having a second spring force. The spring may be a compression spring mounted between a ridge on the drive shaft and the body.

The inner surface of each chuck arm may be configured to engage the bone fixation pin, and the outer surface of each chuck arm may be configured to slidably engage the conical inner surface of the housing.

In various embodiments, the apparatus is configured to insert a bone fixation pin having a rounded or frustoconical head and a body having a cylindrical portion distal to the rounded or frustoconical head, and a body portion having a plurality of planar surfaces proximal to the rounded or frustoconical head. The inner surface of each chuck arm has a slanted lower portion configured to engage the rounded or frustoconical head of the bone fixation pin; and a planar upper portion configured to engage one of the planar surfaces of the bone fixation pin so as to prevent rotation of the bone fixation pin relative to the chuck arms. The proximal end of the drive shaft may have a conical or frustoconical opening configured to receive the rounded or frustoconical head of the bone fixation pin.

In various embodiments, the apparatus is configured to receive a bone fixation pin through the opening in the housing until the head of the pin engages the opening in the proximal end of the drive shaft. Contact between the head of the bone fixation pin and the slanted lower portions of the chuck arm inner surfaces pushes the chuck arms radially outward in the slots in the peripheral edge of the body against the first biasing force. Radial movement of the chuck arms causes the chuck arms to slidably move along the conical inner surface of the housing, pushing the body axially toward the proximal end of the housing against the second biasing force.

Various embodiments disclosed herein relate to an apparatus for inserting a bone fixation pin having a head and a cylindrical body having a body diameter. The apparatus includes a housing having a proximal portion and a distal portion, the distal portion having a stepped inner surface and an opening configured to receive the bone fixation pin; a drive shaft having a proximal end configured to engage a handle and a distal end; and a body having an axis and a peripheral edge. The body may have a bore along its axis, with the bore being configured to slidably engage the distal end of the drive shaft; and a plurality of spaced slots in the peripheral edge of the body. The distal end of the drive shaft and the body may be positioned within the proximal portion of the housing, with the body being biased toward the distal end of the housing by a first biasing force.

A plurality of chuck arms having an inner surface and an outer surface may each be configured to move radially along one of the spaced slots in the peripheral edge of the body, wherein the inner surface of each chuck arm may be configured to engage the bone fixation pin. Each chuck arm may be biased toward the axis of the body by a second biasing force so that the lower tip of each chuck arm slidably engages a first step on the stepped inner surface of the housing.

In various embodiments, the apparatus may be configured to receive a bone fixation pin having a rounded or frustoconical head and a body through the opening in the housing. The distal end of the drive shaft may have a conical or frustoconical opening configured to receive the rounded or frustoconical head of the bone fixation pin. The body of the bone fixation pin may have a cylindrical portion distal to the rounded or frustoconical head, and a body portion having a plurality of planar surfaces proximal to the rounded or frustoconical head. In various embodiments, the inner surface of each chuck arm has a slanted lower portion configured to engage the rounded or frustoconical head of the bone fixation pin; and a planar upper portion configured to engage one of the planar surfaces of the bone fixation pin. the apparatus is configured to receive a bone fixation pin through the opening in the housing until the head of the pin engages the opening in the proximal end of the drive shaft. Contact between the rounded or frustoconical head of the bone fixation pin and the slanted lower portions of the chuck arms pushes the chuck arms toward the proximal end of the housing against the first biasing force. As the chuck arms move toward the proximal end of the housing, the lower tip of each chuck arm is configured to disengage from the first step on the stepped inner surface of the housing and engage a second step on the stepped inner surface. The chuck arms move radially on the body against the second biasing force after disengaging from the first step, until they engage the second step. The planar upper portions of the chuck arms are configured to engage the planar surfaces of the bone fixation pin when the lower tip of each chuck arm engages the second step on the stepped inner surface.

In various embodiments, the stepped inner surface of the housing includes a second step and a third step, with the second step and the third step being configured to be sequentially engaged by the lower tip of each chuck arm as the chuck arms move toward the proximal end of the housing. The chuck arms may be configured to engage the cylindrical body of a bone fixation pin having a first body diameter when the lower tip of each chuck arm engages the second step on the stepped inner surface; and configured to engage the cylindrical body of a bone fixation pin having a second body diameter when the lower tip of each chuck arm engages the third step on the stepped inner surface.

In various embodiments, the body is biased toward the distal end of the housing by a first spring configured to apply the first biasing force; and each chuck arm is biased toward the axis of the body by a second spring configured to apply the second biasing force. The body may be biased toward the distal end of the housing by a compression spring, the compression spring having a first end mounted to the drive shaft and a second end pressing against the body. Each chuck arm may have an outer surface with a spring mounting surface thereon. The chuck arms may be biased toward the axis of the body by a circular garter spring seated on the spring mounting surfaces of the chuck arms.

Various embodiments of the various devices for inserting a bone fixation pin may include a release member, where the release member is configured to disengage the bone fixation pins or screws upon movement of the release member in a proximal direction.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand various exemplary embodiments, reference is made to the accompanying drawings, wherein:

FIG. 1 shows a side view of a first embodiment of a device for inserting a bone fixation pin;

FIG. 2 shows a cross section view of the device for inserting a bone fixation pin of FIG. 1, in the direction of arrows 2 in FIG. 1;

FIG. 3 shows a cross-sectional view of housing 4 of the device of FIG. 1;

FIG. 4 shows a perspective view of the parts of the device of FIG. 1, with housing 4 removed;

FIG. 5 shows a cross-sectional view of housing 4 of the device of FIG. 1, illustrating positioning of chuck arms 15 therein;

FIG. 6 shows an interior view of housing 4 of the device of FIG. 1, illustrating positioning of chuck arms 15 therein;

FIG. 7 shows a perspective view of the body of the device of FIG. 1, with two of the chuck arms 15 attached thereto;

FIG. 8 shows a perspective view of the drive shaft of the device of FIG. 1; and

FIGS. 9 and 10 show views of a second embodiment of the device for inserting a bone fixation pin.

FIG. 11 shows a cross-sectional view of a third embodiment of the device for inserting a bone fixation pin, including a garter spring for biasing chuck arms 15 together.

FIG. 12 shows an exploded view of the third embodiment of FIG. 11.

FIG. 13 shows a cross-sectional view of a fourth embodiment of the device for inserting a bone fixation pin, including leaf springs for biasing chuck arms 15 together.

FIG. 14 shows a view of the housing of the fourth embodiment of FIG. 11.

FIG. 15 shows a cross-sectional view of a fifth embodiment of the device for inserting a bone fixation pin, including an elastic band for biasing chuck arms 15 together.

DETAILED DESCRIPTION

This disclosure described a tool or chuck which receives a bone fixation pin or screw having a shaft, where the shaft may have any of a variety of diameters. The improved chuck includes a plurality of chuck arms which expand radially to grip the shaft of a bone fixation pin or screw without requiring any manipulation of a chuck body or housing by a user. After insertion into a bone, the pin or screw may be withdrawn from the chuck axially, at which point the chuck or tool may receive a second pin or screw having the same diameter or a different diameter.

The foregoing advantages are illustrative of those that can be achieved by the various embodiments disclosed herein and are not intended to be exhaustive or limiting of the possible advantages which can be realized. Thus, these and other advantages of the various embodiments disclosed herein will be apparent from the description herein or can be learned from practicing the various disclosed embodiments, both as embodied herein or as modified in view of any variation that may be apparent to those skilled in the art. Accordingly, the present invention resides in the novel methods, arrangements, combinations, and improvements herein shown and described in various embodiments.

Referring now to the drawings, in which like numerals refer to like components or steps, there are disclosed broad aspects of various exemplary embodiments. FIG. 1 is a side view of a device for inserting a bone fixation pin, having a housing 4 with a cylindrical proximal portion 4 b and a distal portion 4 a with a generally conical outer surface. Drive shaft 1 has a proximal end configured to engage a handle, and a distal end disposed within housing 4. Windows 8 may be positioned in the proximal portion 4 b of housing 4.

The term “bone fixation pin,” as used herein, refers to a pins, wires, screws, and other devices for insertion into bones to fix bone fragments in a desired relative orientation. Exemplary devices include Schanz pins, Steinmann pins, and Schanz screws.

In various embodiments, the proximal end of the drive shaft is configured to engage a handle with an Association for Osteosynthesis-style (AO) quick connect coupling, hereinafter referred to as an AO quick connect coupling. In such embodiments, the proximal end of the drive shaft has a male joint 2 with a planar surface 2 a and a round surface 2 b with a groove 2 c therein. The male joint of the proximal end of the drive shaft engages a female joint on a handle, where the female joint has a corresponding planar surface which engages surface 2 a, and a ball bearing or bearings which fit into groove 2 c. When the planar surface in the female joint engages surface 2 a, rotation of the drive shaft relative to the handle is prevented.

In various embodiments, the device for inserting a bone fixation pin includes a body 3, slidably disposed within housing 4. The outer diameter of body 3 is equal to an inner diameter of a proximal end 4 b of housing 4, allowing body 3 to slidably move within the proximal end 4 b of the housing. As seen in FIG. 1, body 3 is mounted on pin 7. Pin 7 is slidably disposed within slot 6 in drive shaft 1. A spring 9 biases body 3 toward the distal end 4 a of housing 4. However, the inner surface of distal end 4 a of housing 4 has a generally conical shape, which narrows in a distal direction. Due to the conical shape of the distal end 4 a of housing 4, the inner surface of distal end 4 a is narrower than body 3, preventing body 3 from entering the distal end 4 a of housing 4. In some embodiments, the inner surface of distal end 4 a of housing 4 may have a conical shape with a continuous slope. In some embodiments, the inner surface of distal end 4 a of housing 4 may have a conical shape with a discontinuous slope or a plurality of steps.

FIG. 2 shows a cross sectional view of the device of FIG. 1, in the direction of arrows 2 of FIG. 1. The various parts include the drive shaft 1, the body 3, the housing 4, and a plurality of chuck arms 15. Drive shaft 1 includes a cylindrical portion 1 a, a disc-shaped portion 1 b having a diameter d, equal to an inner diameter d of housing 4, and a frustoconical or conical opening 1 c at a distal end of the drive shaft. The disc-shaped portion 1 b of drive shaft 1 is fixed to housing 4 by pin 20. Housing 4 has a cylindrical distal portion 4 b, a conical proximal portion 4 a, and a stepped inner surface 4 c. Body 3 has a ring-shaped portion 3 a having an inner bore and radial slots 3 b; a tubular member 3 c, and second disc shaped member 3 d at the proximal end of body 3. Radial slots 3 b are each configured to slidably receive a chuck arm 15. Body 3 is fixed to pin 7, which is slidably mounted in slot 6 in drive shaft 1, allowing body 3 to move axially in the proximal portion 4 b of housing 4, along drive shaft 1. Stepped inner surface 4 c narrows in a distal direction, preventing body 3 from entering distal portion 4 a of housing 4. Spring 9, mounted between disc shaped portion 1 b of drive shaft 1 and disc shaped member 3 d of body 3, biases the body 3 and the chuck arms 15 mounted in slots 3 b toward the distal end of housing 4, so that the lower tips of chuck arms 15 are surrounded by stepped inner surface 4 c.

FIG. 3 shows a cross-section of housing 4. Housing 4 has a proximal portion 4 b, the proximal portion 4 b having an inner surface with a diameter d, and a conical portion 4 a. Conical portion 4 a of housing 4 has a stepped inner surface, where a stepped surface is defined herein as a surface having multiple steps. As seen in FIG. 3, the housing may have an inner surface with three steps 10, 11, and 12, corresponding to stepped inner surface 4 c as shown in FIG. 2. The step nearest the distal end of the housing, step 10, has a lower surface 10 b sloped toward an axis A of housing 4, and a cylindrical inner surface 10 a which is parallel to axis A. Lower surface 10 b surrounds an opening 14 configured to receive a bone fixation pin. A second step in housing 4, step 11, has a lower surface 11 b sloped toward surface 10 a, and a cylindrical inner surface 11 a which is parallel to axis A, and has a greater diameter than surface 10 a. A third step 12 has a lower surface 12 b sloped toward surface 11 a, and a cylindrical inner surface 12 a having a greater diameter than surface 11 a. The upper edge of surface 12 a meets a conical surface 13 between the stepped surface and the inner surface of the proximal portion 4 b of housing 4. While FIG. 3 shows three steps 10, 11, and 12, the device for inserting a bone fixation pin may have a housing with only two steps on the inner surface of distal portion 4 a, or with four, five, or more steps on the inner surface of distal portion 4 a. Each of the different steps accommodates a different sized bone fixation pin.

FIG. 4 shows the mechanism of the device for inserting a bone fixation pin, with housing 4 removed for clarity. Drive shaft 1 includes a cylindrical portion 1 a, a disc-shaped portion 1 b having a diameter d, equal to the inner diameter d of housing 4, and a frustoconical or conical opening 1 c at a distal end of the drive shaft. Opening 1 c is configured to receive the rounded, conical, or frustoconical end of a bone fixation pin. Body 3 includes a ring-shaped portion 3 a having an inner bore at the distal end of body 3. The outer diameter of the ring-shaped member 3 a is d, equal to the inner diameter d of housing 4. The inner diameter of the ring shaped member 3 a is configured to slidably engage the distal end of drive shaft 1. Disc shaped member 3 a of body 3 has a plurality of slots 3 b, each configured to slidably receive a chuck arm 15. A second disc shaped member 3 d is at the proximal end of body 3, separated by a tubular member 3 c. The drive shaft 1 passes through a common bore through member 3 a, tubular member 3 c, and member 3 b. Spring 9 is mounted between the disc-shaped portion 1 b of drive shaft 1 and disc shaped member 3 d on body 3. Spring 9 biases body 3 toward the distal end of housing 4, away from the disc-shaped portion 1 b of drive shaft 1, which is fixed at the proximal end of housing 1. Body 3 is mounted on pin 7 passing through slot 6 in drive shaft 1 and is able to move axially along drive shaft 1.

A plurality of chuck arms 15 are mounted on body 3, in the radial slots 3 b on disc shaped member 3 d. A T-shaped tab 15 d on each chuck arm 15 fits into one of the slots 3 b, allowing the chuck arms to move radially on body 3. Each chuck arm 15 has a tip with a generally pie-shaped cross section. The tip of each chuck arm 15 has a curved outer surface 15 a, shaped as a segment of a right cylinder. The tip of each chuck arm 15 has an inner surface 15 b which is slanted inwardly, so that the surfaces 15 b on chuck arms 15 collectively form a conical or frustoconical space adapted to receive a conical or frustoconical head of a bone fixation pin, inserted in the direction of arrow B. As the pin moves in the direction of arrow B, force is exerted against surfaces 15 b of chuck arms 15, causing the chuck arms to push body 3 in a proximal direction, against the biasing force applied by spring 9. The force exerted against surfaces 15 b of chuck arms 15 may also cause chuck arms 15 to move outwardly in a radial direction along slots 3 b, until chuck arms 15 have separated sufficiently to allow the conical or frustoconical head of the pin to pass the surfaces 15 b of the chuck arms. At this point, planar surfaces 15 c on the chuck arms 15 engage the body of the bone fixation pin. The pin slides along surfaces 15 c until the head of the pin enters opening 1 c on drive shaft 1. Once it becomes necessary to remove the pin from the chuck arms, the pin may be withdrawn axially from opening 14 in housing 4. Spring 9 then drives body 3 toward the distal end of housing 4, causing chuck arms 15 to move radially inward along the stepped inner surface of housing 4. Chuck arms 15 are then configured to engage a second pin having the same diameter as, or a different diameter from, the first pin.

FIG. 5 shows housing 4, two chuck arms 15 and body 3 positioned within housing 4, and a bone fixation pin 16 entering housing 4 through opening 14 in the direction of arrow B1. As seen in FIG. 5, the outer surface 15 a of each chuck arm forms a section of a cylinder which is coaxial with axis A of housing 4. In the position shown in FIG. 5, outer surface 15 a of each chuck arm rests against cylindrical inner surface 10 a of step 10 in housing 4. Cylindrical inner surface 10 a constrains chuck arms 15, preventing outward radial movement of the chuck arms in slots 3 b of the body 3. Spring force applied by spring 9 (shown in FIG. 4) in the direction of arrow S biases body 3, holding chuck arms 15, against axial movement. The bone fixation pin may have a tubular outer surface along the length of pin 16, with planar surfaces 19 near the proximal end of pin 16. As the pin is inserted into the space 17 defined by planar surfaces 15 c of chuck arms 15, planar surfaces 19 engage planar surfaces 15 c, preventing rotation of pin 16 relative to chuck arms 15.

When bone fixation pin 16 is pushed through opening 14 in housing 4, the head 16 a of pin 16 contacts inner surfaces 15 b of chuck arms 15. Since inner surface 10 a prevents radial movement of chuck arms 15, force applied by pin 16 pushes chuck arms axially against spring force S, in the direction of arrow C. Once the outer surfaces 15 a of chuck arms 15 move axially until they pass surface 10 a, the constraint against radial movement is released. Chuck arm surfaces 15 a then slide along surface 11 b of step 11 in the direction of arrow D, moving both axially against spring force S and radially along slot 3 b in body 3. Radial movement continues until outer surfaces 15 a of chuck arms 15 contact inner surface 11 a of step 11, at which point surface 11 a constrains chuck arms 15 against further radial movement, expanding an opening 17 defined by planar surfaces 15 c of chuck arms 15. If opening 17 is large enough to accommodate the tubular body 16 b of pin 16, body 16 b enters space 17 and planar surfaces 19 on pin 16 are engaged by chuck arm surfaces 15 c. If opening 17 is too small to accommodate tubular body 16 b, pin 16 pushes chuck arms axially until they pass surface 11 a and move radially until the outer surfaces 15 a of chuck arms 15 engage surface 12 a of housing 4, causing opening 17 to expand to accommodate tubular body 16 b. Thus, the device disclosed herein is configured to engage bone fixation pins or screws having different diameters.

FIG. 6 shows an end view of housing 4, showing positioning of chuck arms 15 d within housing 4, when engaging bone fixation pin 16. One of the chuck arms 15 has been partially cut away to show the positioning of the lower tip of the chuck arm, relative to the stepped inner surface of housing 4. As seen in FIGS. 5 and 6, the upper portion of each chuck arm 15 occupies a space defined by body 3 at its upper end, and conical surface 13 of housing 4 at its lower end. The lower tip of each chuck arm 15 extends into the portion of housing 4 including steps 10, 11, and 12. As seen in FIG. 6, the body 16 b of a bone fixation pin occupies a space defined by planar surfaces 15 c of chuck arms 15, with planar surfaces 19 at the proximal end of pin body 16 engaging planar surfaces 15 c to prevent rotation of the pin relative to the chuck arms. As seen in FIG. 6, the cutaway view of one of chuck arms 15 shows that the outer surface 15 a of the tip of each chuck arm 15 rests against cylindrical inner surface 11 a of housing 4, constraining the chuck arm against radial movement so that the bone fixation pin is securely gripped by the chuck arms 15. Once inserted into a bone, the bone fixation pins are removed from the device by withdrawing the pins axially out of hole 14 in housing 4.

FIG. 7 shows body 3 with chuck arms 15 mounted thereon, where one chuck arm has been removed to better show details of the construction of the body and the chuck arms. Each chuck arm 15 is mounted in a radial slot 3 b on body 3, so it may move radially relative to the body. Tubular member 3 b on body 3 is fixed to pin 7. A detailed view of chuck arms 15, showing the shapes of surfaces 15 a. 15 b, and 15 c is presented in FIG. 7.

FIG. 8 provides a view of drive shaft 1, with body 3 mounted thereon (body 3 shown in cross section). As discussed previously, the proximal end of the drive shaft 1 is configured to engage a handle with an AO quick connect coupling and has a male joint 2 with a planar surface 2 a and a round surface 2 b with a groove 2 c therein. Tubular member 1 b is fixed to the proximal end of housing 4. Pin 7, fixed to tubular portion 3 b of body 3, is configured to slide axially in slot 6 on drive shaft 1. Opening 1 c on drive shaft 1 receives the head of a bone fixation pin. As discussed previously, insertion of a bone fixation pin axially in the direction of arrow 4 causes body 3 to move in a proximal direction C in housing 4, against the spring force S applied by spring 9, until the head of the bone fixation pin engages opening 1 c on drive shaft 1.

In a second embodiment shown in FIGS. 9 and 10, a device for inserting a bone fixation pin has a housing 4 with a cylindrical proximal portion 4 b and a distal portion 4 a with a generally conical outer surface. Windows 8 may be positioned in the proximal portion 4 b of housing 4. The device has a drive shaft 1 with a proximal end configured to engage a handle, and a distal end disposed within housing 4. The proximal end of the drive shaft may be configured to engage a handle with an AO quick connect coupling. In such embodiments, the proximal end of the drive shaft has a male joint 2 with a planar surface 2 a and a round surface 2 b with a groove 2 c therein. The male joint of the proximal end of the drive shaft engages a female joint on a handle, where the female joint has a corresponding planar surface which engages surface 2 a. When the planar surface in the female joint engages surface 2, rotation of the drive shaft relative to the handle is prevented.

The device for inserting a bone fixation pin includes a body 3, slidably disposed within housing 4. The outer diameter of body 3 is equal to an inner diameter of housing 4. In the embodiment of FIGS. 9 and 10, body 3 is mounted on pin 7, in a similar fashion to the positioning of body 3 in the embodiment of FIG. 1. Pin 7 is slidably disposed within slot 6 in drive shaft 1. A spring 9 biases body 3 toward the distal end 4 a of housing 4. The conical shape of the distal end 4 a of housing 4 prevents body 3 from entering the distal end of housing 4, in a similar fashion to the stepped inner surface of the distal end of body 4 in the embodiment of FIG. 2. The drive shaft 1 passes through a bore in a tubular release member 21. Drive shaft 1 is fixed to housing 4 by pin 24. Pin 24 passes through slots 21 a in release member 21, allowing release member 21 to move axially relative to housing 4 and drive shaft 1. Chuck arms 23 are visible at an opening 14 in housing 4.

As seen in FIG. 10, body 3 is positioned in housing 4. Body 3 has a ring-shaped portion 3 a having an inner bore and radial slots 3 b; a tubular member 3 c, and a second disc shaped member 3 d at the proximal end of body 3. Radial slots 3 b are each configured to slidably receive a chuck arm 23. Pin 22 secures the body 3 to release member 21, so that body 3 and release member 21 may move axially within housing 4 as a unit. Spring 9 is mounted between a disc shaped portion 1 b of drive shaft 1 and the disc shaped member 3 d of body 3.

As seen in FIG. 10, housing 4 has a distal portion 4 a with a generally conical inner surface 4 d. Chuck arms 23 have a slanted outer surface 23 a which slidably engages the conical inner surface 4 d. If a bone fixation pin is inserted axially in a proximal direction into opening 14 of housing 4 in the direction of arrow B2, the head of the bone fixation pin, which may be rounded, conical, or frustoconical, engages a slanted inner surface 23 b on each chuck arm 23. Application of force to surfaces 23 b pushes the body 3 and the release member 21 in axially in the direction of arrow E, while surfaces 23 a of chuck arms 23 slide along conical inner surface 4 d of body 4, moving in the direction of arrow F. The spacing between chuck arms 23 expands as they move in the direction of arrow F, until the head of the bone fixation pin passes surface 23 b on chuck arms 23, and the body of the bone fixation pin is engaged by inner surfaces 23 c of chuck arm 23. The head of the bone fixation pin is then engaged by conical or frustoconical opening 1 c in drive shaft 1. Spring force S biases body 3 in a proximal direction, and therefore biases chuck arms 15 to move proximally, along conical surface 4 d toward an axis of housing 4. If a bone fixation pin is between chuck arms 23, the force applied by spring 9 biases chuck arms 23 against the pin, maintaining a grip on the pin.

If the release member 21 is pulled in the direction of arrow E prior to inserting a pin, body 3 is pulled and chuck arms 23 are moved in a proximal direction. This releases the constraint on motion of the chuck arms applied by housing inner surface 4 d, increasing the spacing between chuck arms 23 so a bone fixation pin may be inserted directly between the chuck arms 23. Releasing member 21 allows the spring 9 to move body 3 and chuck arms 23 in a distal direction, causing chuck arms to grip the bone fixation pin. If the release member 21 is pulled in the direction of arrow E while a pin is engaged by chuck arms 23, the force applied by spring 9 biasing chuck arms 23 against the pin is released, allowing ready removal of the bone fixation pin.

In a third embodiment shown in FIGS. 11 and 12, a device for inserting a bone fixation pin has a housing 4 with a cylindrical proximal portion 4 b and a distal portion 4 a with a generally conical outer surface and a stepped inner surface, and optional windows 8. The device has a drive shaft 1 with a proximal end configured to engage a handle, and a distal end disposed within housing 4. The proximal end of the drive shaft may be configured to engage a handle, and be equipped with an AO quick connect coupling with a male joint 2 with a planar surface and a round surface, where the planar surface and the round surface are substantially similar to surfaces 2 a and 2 b in FIG. 1, respectively. The round surface on male joint 2 has a groove 2 c therein. The stepped inner surface includes a conical upper portion 13; a stepped intermediate portion defining steps 10, 11, and 12, which increase in diameter toward the proximal end of the housing; and a tubular lower portion defining opening 14 in the distal end of housing 4. The structure of the stepped inner surface is similar to that depicted in FIG. 3 for the first embodiment.

The device for inserting a bone fixation pin includes a body 3, slidably disposed within housing 4. In the embodiment of FIGS. 11 and 12, body 3 is mounted on pin 7, in a similar fashion to the positioning of body 3 in the embodiment of FIG. 1. Pin 7 is slidably disposed within a slot 6 in drive shaft 1. A spring 9 biases body 3 toward the distal end 4 a of housing 4. Spring 9 may be a compression spring with a first end mounted against a ridge 1 b on drive shaft 1 and a second end pressing against disc-shaped member 3 d at an upper end of body 3. Ridge 1 b may be anchored to housing 4.

As seen in FIG. 11, body 3 is positioned in housing 4. Body 3 has a disc-shaped portion 3 a having an inner bore and radial slots 3 b; a tubular member 3 c; and a second disc shaped member 3 d at the proximal end of body 3. Radial slots 3 b are each configured to slidably receive a chuck arm 15.

As seen in FIG. 11, housing 4 has a distal portion 4 a with a stepped inner surface. A plurality of chuck arms 15 are mounted on body 3, in the radial slots 3 b on disc shaped member 3 d. A T-shaped tab 15 d on each chuck arm 15 fits into one of the slots 3 b, allowing the chuck arms to move radially on body 3. Each chuck arm 15 has an outer surface, and a tip with an inner surface 15 b which is slanted inwardly, so that the surfaces 15 b on chuck arms 15 collectively form a conical or frustoconical space adapted to receive a conical or frustoconical head of a bone fixation pin, inserted in the direction of arrow B.

The outer surface of each chuck arm 15 has a spring seating surface 26. A ring-shaped garter spring 25 wraps around the outer surfaces of the various chuck arms 15, so that a portion of the garter spring rests in the spring seating surface 26 of each chuck arm. The garter spring applies a spring force radially inwards against each chuck arm, biasing each chuck arm toward an axis of body 3 in the direction of arrow G. At rest, garter spring 25 draws chuck arms 15 together, toward the axis of body 3. Under such conditions, chuck arms 15 are able to fit within the stepped intermediate portion of the inner surface of housing portion 4 a, with an outer surface of a lower portion of each chuck arm resting agains a cylindrical wall 10 a of step 10 of the stepped region.

As the bone fixation pin (not shown in FIG. 11) is inserted through opening 14 in housing 4 in the direction of arrow B, the head of the pin contacts surface 15 b of each chuck arm. Axial force is exerted against surfaces 15 b of chuck arms 15 in the direction of arrow B, causing the chuck arms to push body 3 in a proximal direction, against the biasing force applied by spring 9, until the lower portion of each chuck arm 15 moves past wall 10 a.

At this point, the head of the pin exerts axial force in the direction of arrow B against surface 15 b of each chuck arm. Further, as there is no constraint against radial movement after the lower portion of each chuck arm 15 passes wall 10 a, the head of the pin exerts radial force against surface 15 b of each chuck arm, away from the axis of body 3, against the biasing force applied by spring 25. The result of this causes the chuck arms to slide along the lower surface 11 b of step 11 of the stepped inner surface of housing 4, until the tip of each chuck arm contacts cylindrical wall 11 a of step 11 of the stepped region. This prevents further radial motion of the chuck arms. At this point, the chuck arms may be spaced sufficiently from each other to allow the head of the bone fixation pin to pass between the chuck arms, so that a longitudinal surface of the pin contacts surface 15 c of each chuck arm, without exerting further axial or radial forces on the chuck arms. The pin then slides between the chuck arms without exerting further radial or axial forces on the chuck arms, until the head of the pin enters frustoconical or conical opening 1 c of drive shaft 1.

If, when the tip of each chuck arm contacts cylindrical wall 11 a of step 11, the chuck arms 15 are not spaced sufficiently from each other to allow the head of the bone fixation pin to pass between surfaces 14 c of chuck arms 15, the head applies further axial force to surface 15 b of each chuck arm. This drives each chuck arm 15 axially until its lower tip clears wall 11 a of step 11. The chuck arms then slide radially along the lower surface 12 b of step 12 of the stepped inner surface of housing 4 due to a radial force against surface 15 b, until the tip of each chuck arm contacts cylindrical wall 12 a of the stepped region, as shown in FIG. 11. At this point, the chuck arms are spaced sufficiently from each other to allow the head of the bone fixation pin to pass between the chuck arms.

As discussed above, garter spring 25 applies a spring force radially inwards on each chuck arm, biasing each chuck arm toward an axis of body 3 in the direction of arrow G. Compression spring 9 applies an axial force driving body 3 distally toward opening 14 in housing 4. It is necessary to control the spring forces applied by these springs.

Garter spring 25 should have a spring force which is sufficient to draw chuck arms inwardly toward an axis of body 3, so that, in the absence of a bone fixation pin, the lower tips of chuck arms sit within a space defined by wall 10 a in housing 4. However, the spring force of garter spring 25 should be low enough to allow the chuck arms to move radially after clearing a cylindrical wall 10 a or 11 a. If the spring force of garter spring 25 is excessively high, radial movement of the chuck arms may be prevented as the body 3 is driven axially against a spring force applied by spring 9.

FIG. 12 shows an exploded view of the embodiment of FIG. 11. The parts of the device include drive shaft 1, which includes a handle 2 with an Association for Osteosynthesis-style (AO) quick connect coupling; a ridge 1 b, and a cylindrical portion 1 a. Body 3 is slidably mounted on cylindrical portion 1 a of drive shaft 1 by pin 7, with pin 7 being slidably engaged by slot 6 on cylindrical portion 1 a. Spring 9 is mounted between ridge 1 b and an upper portion 3 d of body 3. T-shaped tabs 15 d on chuck arms 15 are positioned in slots 3 b of body 3, so as to be slidable in a radial direction. Each chuck arm 15 has a spring seating surface 26. After the chuck arms are mounted in slots 3 b, garter spring 25 is mounted in the spring mounting surfaces 26 of the various chuck arms 15, so that garter spring 25 drives chuck arms 15 radially inward along slots 3 b. This assembly is then positioned within housing 4, and ridge 1 b is fixed to an inner surface of housing 4.

FIG. 13 shows a cross sectional view of an alternate embodiment of a device for inserting a bone fixation pin. The various parts include the drive shaft 1, the body 3, the housing 4, and a plurality of chuck arms 15, generally as shown in FIG. 2. Drive shaft 1 includes a disc-shaped portion 1 b fixed to housing 4 by pin 20. Housing 4 has a cylindrical distal portion 4 b, a conical proximal portion 4 a, and a stepped inner surface 4 c. Body 3 has a ring-shaped portion 3 a having an inner bore and radial slots 3 b, where radial slots 3 b are each configured to slidably receive a chuck arm 15. Body 3 is fixed to pin 7, which is slidably mounted in slot 6 in drive shaft 1, allowing body 3 to move axially in the proximal portion 4 b of housing 4, along drive shaft 1. Slot 6 prevents rotation of body 3 about the drive shaft, which causes each chuck arm to move within the housing along a plane intersecting the center of drive shaft 1.

Leaf spring 27 is mounted on an inner surface of the cylindrical proximal portion 4 b of housing 4. An upper end of a chuck arm 15 contacts leaf spring 27, while leaf spring 27 is fixed to the inner surface of housing 4 at end 27 a. Leaf spring 27 biases the chuck arm 15 toward an axis of drive shaft 1. Leaf spring 27 has a wedge-shaped surface 27 b which contacts chuck arm 15. As a chuck arm is pushed axially by insertion of a bone fixation pin in the direction of arrow B, the chuck arm moves past spring 27, pushing the wedge-shaped surface 27 b toward the inner surface of housing 4. This causes the spring force on the chuck arm 15 from spring 27 to gradually increase as the chuck arm moves in a proximal direction, increasing the biasing force pushing the chuck arm toward the drive shaft. Preferably, each chuck arm interacts with a separate leaf spring 27. FIG. 14 shows a cross sectional view of a housing 4 for a device for inserting a bone fixation pin, designed for use with three chuck arms equally spaced from each other. The housing 4 includes leaf springs 27 mounted to the inner wall of the housing, spaced 120° from each other.

In another embodiment shown in FIG. 15, a device for inserting a bone fixation pin has a housing 4 with a cylindrical proximal portion 4 b and a distal portion 4 a with a generally conical outer surface and a stepped inner surface. The device has a drive shaft 1 with a proximal end configured to engage a handle, and a distal end disposed within housing 4. The stepped inner surface includes a conical upper portion 13; a stepped intermediate portion defining steps 10, 11, and 12, which increase in diameter toward the proximal end of the housing; and a tubular lower portion defining opening 14 in the distal end of housing 4.

The device for inserting a bone fixation pin includes a body 3, slidably disposed within housing 4. In the embodiment of FIG. 15, body 3 is mounted on pin 7, which is slidably disposed within a slot 6 in drive shaft 1. A spring 9 biases body 3 toward the distal end 4 a of housing 4. Spring 9 may be a compression spring with a first end mounted against a ridge 1 b on drive shaft 1 and a second end pressing against disc-shaped member 3 d at an upper end of body 3. Ridge 1 b may be anchored to housing 4.

As seen in FIG. 15, body 3 is positioned in housing 4. Body 3 has a disc-shaped portion 3 a having an inner bore and radial slots 3 b; a tubular member 3 c; and a second disc shaped member 3 d at the proximal end of body 3. Radial slots 3 b are each configured to slidably receive a chuck arm 15.

As seen in FIG. 15, housing 4 has a distal portion 4 a with a stepped inner surface. A plurality of chuck arms 15 are mounted on body 3, in the radial slots 3 b on disc shaped member 3 d. A ring-shaped elastic band 28 wraps around the outer surfaces of the various chuck arms 15. The elastic band 28 applies a biasing force radially inwards against each chuck arm, biasing each chuck arm toward an axis of body 3 in the direction of arrow G. At rest, elastic band 28 draws chuck arms 15 together, toward the axis of body 3.

As a bone fixation pin (not shown in FIG. 15) is inserted through opening 14 in housing 4 in the direction of arrow B, the head of the pin contacts surface 15 b of each chuck arm. Axial force is exerted against surfaces 15 b of chuck arms 15 in the direction of arrow B, causing the chuck arms to push body 3 in a proximal direction, against a biasing force applied by spring 9, until the lower portion of each chuck arm 15 moves past wall 10 a.

At this point, the head of the pin exerts axial force in the direction of arrow B against surface 15 b of each chuck arm. Further, as there is no constraint against radial movement after the lower portion of each chuck arm 15 passes wall 10 a, the head of the pin exerts radial force against surface 15 b of each chuck arm, away from the axis of body 3, against the biasing force applied by spring 25. The result of this causes the chuck arms to slide along the lower surface 11 b of step 11 of the stepped inner surface of housing 4, until the tip of each chuck arm contacts cylindrical wall 11 a of step 11 of the stepped region. This prevents further radial motion of the chuck arms.

As discussed above, elastic band 28 applies a biasing force radially inwards on each chuck arm, biasing each chuck arm toward an axis of body 3 in the direction of arrow G. Compression spring 9 applies an axial biasing force driving body 3 distally toward opening 14 in housing 4. It is necessary to control these biasing forces.

Elastic band 28 should apply a biasing force which is sufficient to draw chuck arms inwardly toward an axis of body 3, so that, in the absence of a bone fixation pin, the lower tips of chuck arms sit within a space defined by wall 10 a in housing 4. However, the biasing force of elastic band 28 should be low enough to allow the chuck arms to move radially after being pushed axially past a cylindrical wall 10 a or 11 a. If the biasing force of elastic band 28 is excessively high, radial movement of the chuck arms may be prevented as the body 3 is driven axially against a spring force applied by spring 9.

Although the various exemplary embodiments have been described in detail with particular reference to certain exemplary aspects thereof, it should be understood that the invention is capable of other embodiments and its details are capable of modifications in various obvious respects. As is readily apparent to those skilled in the art, variations and modifications can be affected while remaining within the spirit and scope of the invention. Accordingly, the foregoing disclosure, description, and figures are for illustrative purposes only and do not in any way limit the invention, which is defined only by the claims. 

What is claimed is:
 1. An apparatus for inserting a bone fixation pin having a head and a cylindrical body having a body diameter, said apparatus comprising: a housing having a proximal portion and a distal portion, the distal portion having a stepped inner surface and an opening configured to receive the bone fixation pin; a drive shaft having a proximal end configured to engage a handle and a distal end; a body having an axis and a peripheral edge, said body comprising: a bore along the axis, said bore being configured to slidably engage the distal end of the drive shaft; and a plurality of spaced slots in the peripheral edge of the body; and wherein the distal end of the drive shaft and the body are within the proximal portion of the housing, the body being biased toward the distal end of the housing by a first biasing force; and a plurality of chuck arms having an inner surface and an outer surface, each chuck arm being configured to move radially along one of the spaced slots in the peripheral edge of the body, wherein the inner surface of each chuck arm is configured to engage the bone fixation pin, each chuck arm being biased toward the axis of the body by a second biasing force so that the lower tip of each chuck arm slidably engages a first step on the stepped inner surface of the housing.
 2. The apparatus of claim 1, wherein the apparatus is configured to insert a bone fixation pin having a rounded or frustoconical head and a body having: the cylindrical portion distal to the rounded or frustoconical head, and a body portion having a plurality of planar surfaces proximal to the rounded or frustoconical head; wherein the inner surface of each chuck arm has: a slanted lower portion configured to engage the rounded or frustoconical head of the bone fixation pin; and a planar upper portion configured to engage one of the planar surfaces of the bone fixation pin.
 3. The apparatus of claim 2, wherein the distal end of the drive shaft has a conical or frustoconical opening configured to receive the rounded or frustoconical head of the bone fixation pin.
 4. The apparatus of claim 3, wherein the apparatus is configured to receive a bone fixation pin through the opening in the housing until the head of the pin engages the conical or frustoconical opening in the distal end of the drive shaft; wherein contact between the conical or frustoconical head of the bone fixation pin and the slanted lower portions of the chuck arms pushes the chuck arms toward the proximal end of the housing against the first biasing force; and wherein the lower tip of each chuck arm is configured to disengage from the first step on the stepped inner surface of the housing and engage a second step on the stepped inner surface as the chuck arms move toward the proximal end of the housing; wherein planar upper portions of the chuck arms are configured to engage the planar surfaces of the bone fixation pin when the lower tip of each chuck arm engages the second step on the stepped inner surface.
 5. The apparatus of claim 4, wherein the lower tip of each chuck arm is configured to: disengage from the first step on the stepped inner surface of the housing: and engage the second step on the stepped inner surface; wherein the chuck arms move radially on the body against the second biasing force after disengaging from the first step.
 6. The apparatus of claim 4, wherein the stepped inner surface of the housing comprises a second step and a third step, said second step and said third step being configured to be sequentially engaged by the lower tip of each chuck arm as the chuck arms move toward the proximal end of the housing; wherein the chuck arms are configured to engage the cylindrical body of a bone fixation pin having a first body diameter when the lower tip of each chuck arm engages the second step on the stepped inner surface; and wherein the chuck arms are configured to engage the cylindrical body of a bone fixation pin having a second body diameter when the lower tip of each chuck arm engages the third step on the stepped inner surface.
 7. The apparatus of claim 1, wherein the body is biased toward the distal end of the housing by a first spring configured to apply the first biasing force; and each chuck arm is biased toward the axis of the body by a second spring configured to apply the second biasing force.
 8. The apparatus of claim 7, wherein the body is biased toward the distal end of the housing by the first spring, the first spring being a compression spring, the compression spring having a first end mounted to the drive shaft and a second end pressing against the body.
 9. The apparatus of claim 7, wherein each chuck arm has an outer surface with a spring mounting surface thereon; and the chuck arms are biased toward the axis of the body by the second spring, the second spring being a circular garter spring seated on the spring mounting surfaces of the chuck arms.
 10. The apparatus of claim 1, wherein the body is biased toward the distal end of the housing by a first spring configured to apply the first biasing force; and each chuck arm is biased toward the axis of the body by a leaf spring mounted on an inner surface of the proximal portion of the housing, the leaf spring being configured to apply the second biasing force.
 11. The apparatus of claim 1, wherein the body is biased toward the distal end of the housing by a first spring configured to apply the first biasing force; and the chuck arms are biased toward the axis of the body by an elastic band engaging an outer surface of each chuck arm, the elastic band being configured to apply the second biasing force. 